8.b Task 2: Nanoparticle contrast agents (Greg Lanza) 8.b.1 Specific aims The role of angiogenesis in lymph node metastasis has received little attention, but several studies point to the association of tumor induced lymphangiogenesis and the expression of vascular endothelial growth factor (VEGF)-A, -C, and platelet derived growth factor (PDGF) [126-128]. Current evidence in animal models and corroborated in human axial lymph nodes from patients with breast cancer indicates that the establishment of metastases in the SLN is preceded by vascular reorganization induced by the primary tumor [129]. The architecture of the SLN is enriched with functional blood vessels derived from rapidly proliferating high endothelial venules in response to proangiogenic cytokines elaborated by the primary tumor. The neovascular rich lymph node create a fertile "soil" for metastatic cancer cells to seed and grow [129]. Various forms of integrins such as av|J3, avp5. anda5pi are up regulated in angiogenic blood vessels and these proteins can be targeted effectively with RGD (Arginine-Glycine-Aspartic acid) peptides or high affinity peptidomimetic. In particular, biocompatible perfluorocarbon (PFC)-based nanoparticles have been developed by the project leader for imaging the expression of integrins in vivo. In addition to its excellent biocompatibility profile in animals and humans, MRI can image PFC nanoparticles and formulations that include fluorescent dyes have been used for optical imaging applications. MRI is capable of imaging the neovascular bed of axillary lymph nodes with high resolution imaging in a depth-independent, tomographic manner. Therefore, we will develop multimodal perfluorocarbon-based nanoparticles that are safe for use in humans. The particles can be administered peri-tumorally for direct SLN imaging or systemically (i.v.) for imaging lymph node angiogenic vessels. The PFC nanoparticles have the added advantage of imaging the vascular system of the lymph nodes by both MRI and PAT methods and adds molecular information to PAT data. The Specific Aims for this project are to: (1) Optimize formulation of multimodal and biocompatible PFC nanoparticles for PAT, and MRI scanning of SLN and associated neovascular system. (2) Image lymph nodes by both PAT and MRI in mice. We will use a highly proliferating tumor model (4T1Luc tumor) that expresses high levels of av(33 integrins and neovascular systems for this study. The Support Core will perform the MRI studies and the PAT imaging will be carried as described in Sections 8.c and 8.d (see 8.a above for additional information).